Change division in TensorFlow to flooring semantics.

- tf.div changes to new behavior, but it will be deprecated
- tf.divide is currently a synonym for tf.div but will remain
- tf.mod changes to new behavior, but it will be deprecated,
  you can use % or tf.floormod in the future.
- the op FloorDiv now is extended to work on reals
Change: 139922734

7 files changed, 120 insertions, 8 deletions

diff --git a/RELEASE.md b/RELEASE.md
index d618c865f5..939eee0f2d 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -2,6 +2,10 @@
 
 ## Breaking Changes to the API
 
+* Division and modulus operators (/, //, %) now match Python (flooring)
+  semantics. tf.div is renamed to tf.division. New operators tf.truncatediv and
+  tf.truncatemod are available for achieving the previous C++ (truncation)
+  division/modulus semantics.
 * `BusAdjacency` enum replaced with a protocol buffer `DeviceLocality`.  PCI bus
 indexing now starts from 1 instead of 0, and bus_id==0 is used where previously
 BUS_ANY was used.
diff --git a/tensorflow/core/kernels/cwise_op_floor_div.cc b/tensorflow/core/kernels/cwise_op_floor_div.cc
index 7930d83413..a5767476c3 100644
--- a/tensorflow/core/kernels/cwise_op_floor_div.cc
+++ b/tensorflow/core/kernels/cwise_op_floor_div.cc
@@ -28,9 +28,13 @@ REGISTER5(BinaryOp, CPU, "FloorDiv", functor::safe_floor_div, uint8, uint16,
 TF_CALL_INTEGRAL_TYPES(REGISTER_SYCL_KERNEL);
 #undef REGISTER_SYCL_KERNEL
 #endif // TENSORFLOW_USE_SYCL
+REGISTER3(BinaryOp, CPU, "FloorDiv", functor::floor_div_real, float,
+          Eigen::half, double);
 #if GOOGLE_CUDA
 REGISTER4(BinaryOp, GPU, "FloorDiv", functor::floor_div, uint8, uint16, int16,
           int64);
+REGISTER3(BinaryOp, GPU, "FloorDiv", functor::floor_div_real, float,
+          Eigen::half, double);
 #endif
 
 #if GOOGLE_CUDA
diff --git a/tensorflow/core/kernels/cwise_op_gpu_floor_div.cu.cc b/tensorflow/core/kernels/cwise_op_gpu_floor_div.cu.cc
index 1300bf2232..0e4887eafd 100644
--- a/tensorflow/core/kernels/cwise_op_gpu_floor_div.cu.cc
+++ b/tensorflow/core/kernels/cwise_op_gpu_floor_div.cu.cc
@@ -20,6 +20,7 @@ limitations under the License.
 namespace tensorflow {
 namespace functor {
 DEFINE_BINARY5(floor_div, uint8, uint16, int16, int32, int64);
+DEFINE_BINARY3(floor_div_real, Eigen::half, float, double);
 }  // namespace functor
 }  // namespace tensorflow
 
diff --git a/tensorflow/core/kernels/cwise_ops.h b/tensorflow/core/kernels/cwise_ops.h
index 7f35e03feb..34103347fb 100644
--- a/tensorflow/core/kernels/cwise_ops.h
+++ b/tensorflow/core/kernels/cwise_ops.h
@@ -269,6 +269,24 @@ struct functor_traits<google_floor_div<Scalar>> {
   };
 };
 
+// TODO(b/32239616): This kernel should be moved into Eigen and vectorized.
+template <typename T, typename Enable = void>
+struct google_floor_div_real {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T operator()(const T& x,
+                                                           const T& y) const {
+    return Eigen::numext::floor(x / y);
+  }
+};
+
+template <typename Scalar>
+struct functor_traits<google_floor_div_real<Scalar>> {
+  enum {
+    Cost = 2 * Eigen::internal::scalar_div_cost<Scalar, false>::value +
+           2 * NumTraits<Scalar>::AddCost,
+    PacketAccess = false
+  };
+};
+
 // TODO(b//32239616): This kernel should be moved into Eigen and vectorized.
 template <typename T>
 struct google_floor_fmod {
@@ -612,6 +630,9 @@ struct safe_floor_div : base<T, Eigen::internal::safe_div_or_mod_op<
 };
 
 template <typename T>
+struct floor_div_real : base<T, Eigen::internal::google_floor_div_real<T>> {};
+
+template <typename T>
 struct pow : base<T, Eigen::internal::scalar_binary_pow_op_google<T, T>> {};
 
 template <typename T>
diff --git a/tensorflow/python/ops/math_grad.py b/tensorflow/python/ops/math_grad.py
index 1fd69ae717..3502f11892 100644
--- a/tensorflow/python/ops/math_grad.py
+++ b/tensorflow/python/ops/math_grad.py
@@ -613,16 +613,48 @@ def _MulGrad(op, grad):
 
 @ops.RegisterGradient("Div")
 def _DivGrad(op, grad):
+  """The gradient for the Div operator."""
   x = op.inputs[0]
   y = op.inputs[1]
   sx = array_ops.shape(x)
   sy = array_ops.shape(y)
-  rx, ry = gen_array_ops._broadcast_gradient_args(sx, sy)  # pylint: disable=protected-access
+  # pylint: disable=protected-access
+  rx, ry = gen_array_ops._broadcast_gradient_args(sx, sy)
+  # pylint: enable=protected-access
+  x = math_ops.conj(x)
+  y = math_ops.conj(y)
+  return (array_ops.reshape(math_ops.reduce_sum(math_ops.div(grad, y), rx), sx),
+          array_ops.reshape(math_ops.reduce_sum(
+              grad * math_ops.div(-x, math_ops.square(y)), ry), sy))
+
+
+@ops.RegisterGradient("FloorDiv")
+def _FloorDivGrad(_, unused_grad):
+  """The gradient for the FloorDiv operator."""
+  return None, None
+
+
+@ops.RegisterGradient("TruncateDiv")
+def _TruncateDivGrad(_, unused_grad):
+  return None, None
+
+
+@ops.RegisterGradient("RealDiv")
+def _RealDivGrad(op, grad):
+  """RealDiv op gradient."""
+  x = op.inputs[0]
+  y = op.inputs[1]
+  sx = array_ops.shape(x)
+  sy = array_ops.shape(y)
+  # pylint: disable=protected-access
+  rx, ry = gen_array_ops._broadcast_gradient_args(sx, sy)
+  # pylint: enable=protected-access
   x = math_ops.conj(x)
   y = math_ops.conj(y)
-  return (array_ops.reshape(math_ops.reduce_sum(grad / y, rx), sx),
-          array_ops.reshape(math_ops.reduce_sum(grad *
-                                         (-x / math_ops.square(y)), ry), sy))
+  return (array_ops.reshape(math_ops.reduce_sum(
+      math_ops.realdiv(grad, y), rx), sx),
+          array_ops.reshape(math_ops.reduce_sum(
+              grad * math_ops.realdiv(-x, math_ops.square(y)), ry), sy))
 
 
 @ops.RegisterGradient("Pow")
diff --git a/tensorflow/python/ops/math_ops.py b/tensorflow/python/ops/math_ops.py
index c2aab4c945..6fce264bd9 100644
--- a/tensorflow/python/ops/math_ops.py
+++ b/tensorflow/python/ops/math_ops.py
@@ -928,7 +928,32 @@ def truediv(x, y, name=None):
     if dtype is not None:
       x = cast(x, dtype)
       y = cast(y, dtype)
-    return gen_math_ops.div(x, y, name=name)
+    return gen_math_ops.real_div(x, y, name=name)
+
+
+def div(x, y, name=None):
+  with ops.name_scope(name, "truediv", [x, y]) as name:
+    x = ops.convert_to_tensor(x, name="x")
+    y = ops.convert_to_tensor(y, name="y", dtype=x.dtype.base_dtype)
+    x_dtype = x.dtype.base_dtype
+    y_dtype = y.dtype.base_dtype
+    if x_dtype != y_dtype:
+      raise TypeError("x and y must have the same dtype, got %r != %r" %
+                      (x_dtype, y_dtype))
+    if x_dtype.is_floating or x_dtype.is_complex:
+      return gen_math_ops.real_div(x, y, name=name)
+    else:
+      return gen_math_ops.floor_div(x, y, name=name)
+
+
+def div_deprecated(x, y, name=None):
+  return gen_math_ops.div(x, y, name)
+
+mod = gen_math_ops.floor_mod
+
+
+def mod_deprecated(x, y, name=None):
+  return gen_math_ops.mod(x, y, name)
 
 
 # TODO(aselle): Deprecate this once all internal functionality uses
@@ -960,6 +985,11 @@ def floordiv(x, y, name=None):
     TypeError: If the inputs are complex.
   """
   with ops.name_scope(name, "floordiv", [x, y]) as name:
+    return gen_math_ops.floor_div(x, y, name=name)
+
+
+def floordiv_deprecated(x, y, name=None):
+  with ops.name_scope(name, "floordiv", [x, y]) as name:
     x = ops.convert_to_tensor(x, name="x")
     dtype = x.dtype
     if dtype.is_floating:
@@ -971,7 +1001,6 @@ def floordiv(x, y, name=None):
       # return gen_math_ops.floor_div(x, y, name=name)
       return gen_math_ops.div(x, y, name=name)
 
-
 realdiv = gen_math_ops.real_div
 truncatediv = gen_math_ops.truncate_div
 # TODO(aselle): Rename this to floordiv when we can.
@@ -1002,12 +1031,12 @@ _OverrideBinaryOperatorHelper(gen_sparse_ops.sparse_dense_cwise_mul, "mul",
 _OverrideBinaryOperatorHelper(gen_math_ops.add, "add")
 _OverrideBinaryOperatorHelper(gen_math_ops.sub, "sub")
 _OverrideBinaryOperatorHelper(_mul_dispatch, "mul")
-_OverrideBinaryOperatorHelper(gen_math_ops.div, "div")
+_OverrideBinaryOperatorHelper(div, "div")
 _OverrideBinaryOperatorHelper(truediv, "truediv")
 _OverrideBinaryOperatorHelper(floordiv, "floordiv")
 # TODO(aselle): Switch mod to floor_mod when ready
 # _OverrideBinaryOperatorHelper(gen_math_ops.floor_mod, "mod")
-_OverrideBinaryOperatorHelper(gen_math_ops.mod, "mod")
+_OverrideBinaryOperatorHelper(gen_math_ops.floor_mod, "mod")
 _OverrideBinaryOperatorHelper(pow, "pow")
 
 
diff --git a/tensorflow/python/ops/math_ops_test.py b/tensorflow/python/ops/math_ops_test.py
index 4bbbc7b4f7..197ddb6a75 100644
--- a/tensorflow/python/ops/math_ops_test.py
+++ b/tensorflow/python/ops/math_ops_test.py
@@ -24,6 +24,7 @@ from tensorflow.python.framework import constant_op
 from tensorflow.python.framework import ops
 from tensorflow.python.framework import test_util
 from tensorflow.python.ops import array_ops
+from tensorflow.python.ops import gradients
 from tensorflow.python.ops import math_ops
 from tensorflow.python.ops import variables
 from tensorflow.python.platform import googletest
@@ -305,6 +306,26 @@ class DivAndModTest(test_util.TensorFlowTestCase):
       np_result = np.divide(nums, divs)
       self.assertAllEqual(tf_result, np_result)
 
+  def testComplexDiv(self):
+    foo = array_ops.constant([1.+3.j])
+    with self.test_session():
+      _ = math_ops.div_deprecated(foo, 1.).eval()
+      _ = math_ops.div(foo, 2.).eval()
+
+  def testFloorDivGrad(self):
+    with self.test_session():
+      a = variables.Variable(2.)
+      b = variables.Variable(4.)
+      with self.test_session() as sess:
+        sess.run(variables.initialize_all_variables())
+        c_grad = gradients.gradients(math_ops.div_deprecated(a, b), [a, b])
+        self.assertAllEqual([x.eval() for x in c_grad], [.25, -.125])
+        c_grad = gradients.gradients(math_ops.div(a, b), [a, b])
+        self.assertAllEqual([x.eval() for x in c_grad], [.25, -.125])
+        c_grad = gradients.gradients(math_ops.floordiv(a, b), [a, b])
+        self.assertAllEqual([None if x is None else x.eval() for x in c_grad],
+                            [None, None])
+
   def testConsistent(self):
     nums, divs = self.intTestData()
     with self.test_session():